8 hours really is a lot of time to work for free. They are basically expecting you to dedicate some of your spare time to doing work for them. To me, this mean

8 hours really is a lot of time to work for free. They are basically expecting you to dedicate some of your spare time to doing work for them. To me, this means the company does not value my own time, and it might even be a red flag which indicates unhealthy expectations about your work-life balance. If they had an assignment which would take about an hour, maybe two, fine. But any more than that and I think you should be paid for that.